Low Poly Modern (2018) Standards?
The term standard is not used in the sense you think. It's not like an SI units standard or sRGB (literally meaning standard red green blue) standard. There is no definition for lowpoly, other than it needs to display in real-time. It depends on hardware.

By modern standards (standards in hadrware) it is safe to say that the dolphin can be rendered in real-time and so would be considered low poly.

By ancient standards (4bit computer the size of a room) you wouldn't be able to render that at 60fps, it would be considered high poly.